Low cost, high performance radar networks

ABSTRACT

A real-time radar surveillance system comprises at least one land-based non-coherent radar sensor apparatus adapted for detecting maneuvering targets and targets of small or low radar cross-section. The radar sensor apparatus includes a marine radar device, a digitizer connected to the marine radar device for receiving therefrom samples of radar video echo signals, and computer programmed to implement a software-configurable radar processor generating target data including detection data and track data, the computer being connectable to a computer network including a database. The processor is figured to transmit at least a portion of the target data over the network to the database, the database being accessible via the network by at least one user application that receives target data from the database, the user application providing a user interface for at least one user of the system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 12/932,593 filedMar. 1, 2011, now U.S. Pat. No. 8,384,585, in turn a division ofapplication Ser. No. 11/110,436 filed Apr. 20, 2005, now U.S. Pat. No.7,740,206.

FIELD OF THE INVENTION

This invention relates to land-based radar surveillance of wide areas orlocal sites. It also relates to radar detection and tracking andmulti-sensor fusion.

BACKGROUND OF THE INVENTION

“Homeland Security” refers to the goal of detecting and defendingagainst threats to public safety posed by potential attack by hostileindividuals or groups. Homeland Security applications for radarsurveillance differ fundamentally from most military applications. Thehigh price of military radars is justified by the critical and urgentneed for protection in combat zones or near high-value assets. The priceis affordable because the deployments are confined in time and/or space.Homeland Security, in contrast, deals with threats, such as terroristattacks, that materialize infrequently and can occur anywhere.Surveillance to counter such threats must be deployed simultaneouslyacross huge areas on a permanent 24/7 basis. Therefore, in the marketfor sensors used for Homeland Security surveillance, low-cost is notjust a competitive advantage, it is a fundamental requirement.

Homeland Security includes such applications as border patrol, lawenforcement, critical infrastructure protection (both corporate andpublic facilities), transportation security, port security and coastalsurveillance. All of these applications require cost-effective detectionand tracking of small, fast, maneuvering, elusive targets. Targets ofinterest include (but are not limited to) small watercraft in littoralregions, and snowmobiles on snow or ice cover, or other vehicles. At thepresent time, low-cost radar systems suitable for these homelandsecurity applications are not operational.

Altogether different problems that also require cost-effective detectionand tracking of small, fast, maneuvering, elusive targets are the birdair strike hazard (BASH) problem and the natural resource management(NRM) problem concerning birds. Billions of dollars in damage toaircraft and significant loss of life have been recorded due to birdsflying into aircraft, particularly during take-off and landing in thevicinity of airports. At the present time, low-cost radar systemssuitable for these avian radar applications are under development.

Practical solutions for the aforementioned applications must be able toprovide continuous, day or night, all weather, wide-area situationalawareness with automated detection, localization and warnings ofthreats. The wide-area situational awareness points towards a network ofradars operating together to provide a composite picture. The automatedwarning of threats points toward high-quality target track data withsophisticated criteria to determine suspicious or potentially dangeroustarget behavior, as well as communication of alerts to users who requirethat information. Furthermore, practical solutions must also minimizeoperator interaction due to the fact that system cost includes the costof human labor needed to operate the system. Some of the keyrequirements of the cited applications include:

-   -   Low-cost, high-performance radar antennas and transceivers that        can be mounted on land-based towers as well as on mobile        vehicles and vessels.    -   Radar processing that can reliably detect and track small,        low-RCS, maneuvering targets in dense target and clutter        environments.    -   Automatic threat detection and alert capability to remote users    -   The formation of radar networks to provide wide-area coverage    -   Low cost of operation    -   Low life cycle costs    -   Data and analysis support for research and development

While X-band or S-band coherent radar technology used in air trafficcontrol and military radars could be integrated, reconfigured andoptimized to satisfy performance requirements for the aforementionedapplications, such systems would not be affordable. Typically, eachradar sensor would cost in the millions of dollars, not taking intoaccount the life cycle costs of maintaining and operating such systems.The purpose of the invention disclosed herein is to provide a low-costradar surveillance solution to these problems, where the radar sensorwould cost as little as $50,000 or less.

Commercial, off-the-shelf (COTS) marine radars (from companies such asFuruno, Raymarine, Decca, etc.) are very inexpensive due to the factthat they are noncoherent and that millions of them are sold world-widefor use on commercial and recreational vessels. A radar antenna andtransceiver can be purchased for under $10,000, depending on thetransmitter power and antenna selected. These marine radars exhibitsurprisingly good hardware specifications such as transmitter power,receiver characteristics and antenna pattern. However, in operation,these radars deliver mediocre performance for our targets of interestbecause of their primitive signal processing. They are primarily usedfor detecting large vessels and shoreline for navigation and collisionavoidance purposes.

Combining a COTS marine radar with a digitizer board and a softwareradar processor that runs on a COTS personal computer (PC) can allow amarine radar to be adapted for other applications. One vendor [RutterTechnologies, www.ruttertech.com] has developed a radar processor forsuch a system [the Sigma S6 Processor] where the radar processor istuned for detecting slow-moving floating ice targets (such as ice bergsor bergy bits) in the sea by using scan-to-scan integration techniquesover time frames of 20 seconds to 160 seconds (to improve signal toclutter ratio (SCR)) combined with an alpha-beta tracker designed fornon-maneuvering targets. This system has been designed for maritimeoperation on-board a vessel or moored platform and hence does not dealwith the formation of radar networks, does not solve the small-RCS,fast, maneuvering target problem, and does not provide low-cost ofoperation since an operator is needed for each system. In addition,alerts are not automatically provided to remote users for unattendedoperation.

OBJECTS OF INVENTION

The objects of the present invention concern radar surveillance networksapplied to homeland security and avian radar applications.

A primary object of the present invention is to provide a land-based,radar system that is low-cost and high-performance for HomelandSecurity, BASH and NRM applications.

Another object of the present invention is to develop sophisticatedradar signal and data processing algorithms that can reliably detect andtrack small, low-RCS, maneuvering targets, including small watercraft,snowmobiles, birds and aircraft, in dense target and clutterenvironments.

Another object of the present invention is to provide a low-cost, highperformance radar sensor that can be networked with other like anddissimilar sensors to form low-cost, high-performance radar networkswith situational awareness and wide-area coverage.

Another key object of the present invention is to use sophisticatedradar processing combined with spatial diversity (associated with thelocation of radar sensors making up a radar network), which allows theperformance of a low-cost, noncoherent radar system to approach that ofmuch more expensive coherent radar systems.

Another object of the present invention is to take advantage ofstandardized COTS technologies to the maximum extent possible to keepthe system cost low and to provide for low life cycle costs associatedwith maintainability, upgrade ability and training.

Another object of the present invention is that COTS marine radars areused as the radar sensor in order to minimize sensor costs.

Yet another object of the present invention is that the radar sensorsand systems are software-configurable so as to allow them to be easilyadapted for different applications.

An object of the present invention is that operator interaction isminimized in order to reduce the cost of operation.

Yet another object of the present invention is that the radar sensorsand system can be controlled remotely.

Another key object of the present invention is that it supports remoteusers with different user requirements.

Yet another object of the invention is that it can provide automatedthreat detection and issue alerts to local and remote users.

Another object of the present invention is that radar target data aregeo-referenced using a geographic information system (GIS) so thattarget data is tagged to earth co-ordinates and target dynamicsincluding speed and heading are provided.

Yet another object of the present invention is that the radar systemincorporates features that efficiently support research and developmentand off-line analysis, allowing for example, target behavior to bestudied so that target classification algorithms can be developed, orallowing target data to be studied and replayed after the fact, toassist, for example, in the prosecution of terrorists.

These and other objects of the invention will be apparent from thedrawings and descriptions included herein. It is to be noted that eachobject of the invention is achieved by at least one embodiment of theinvention. However, it is not necessarily the case that every embodimentof the invention meets every object of the invention as discussedherein.

SUMMARY OF THE INVENTION

The present invention relates to the design of a low-cost,high-performance, land-based radar sensor and a radar network consistingof one or more of these radar sensors designed for homeland security andavian radar applications. These challenging applications and some of thefeatures and performance of the present invention have been reported in[Weber, P et al., Low-cost radar surveillance of inland waterways forhomeland security applications, 2004 IEEE Radar Conference, Apr. 26-29,2004, Philadelphia, Pa.] and [Nohara, T J et al, Affordable avian radarsurveillance systems for natural resource management and BASHapplications, 2005 IEEE International Radar Conference, May 9-12, 2005,Arlington, Va.], respectively, which are incorporated herein byreference.

A feature of the present invention is the preferred use of COTS marineradars to provide economical antennas and transceivers that operate atX-band and S-band. COTS marine radars exhibit surprisingly good hardwarespecifications such as transmitter power, receiver characteristics andantenna pattern. However, in operation (for homeland security and avianradar applications) these radars deliver mediocre performance because oftheir primitive signal processing. The first part of our invention is tocreate an inexpensive radar sensor with high performance by integratinga sophisticated radar processor with COTS marine radar equipment. Theradar processor itself incorporates sophisticated algorithms andsoftware that runs preferably on COTS personal computers (PC) to keepcosts down. The system design of the invention described hereindemonstrates that affordable COTS marine radars combined with COTSpersonal computers (PCs) with specialized software can provide powerfulsurveillance systems.

For the cited applications, which are the focus of this disclosure,targets of interest include small watercraft, snowmobiles, and birds.These small, fast moving and maneuvering, non-cooperative targets havelow (and fluctuating) radar cross-Sections (RCS), and compete withground (e.g. land, snow, ice cover, urban features), water and weatherclutter. COTS marine radars are designed for navigation and recreationaluse and, as such, have low small-target detection sensitivity. Thepresence of many friendly targets further complicates matters and thetracking circuits included with these radars are completely inadequatefor our targets of interest. To detect these small targets with thesemarine radars, surveillance operators would need to observe the displayover several consecutive radar scans in order to begin to assess thesituation at hand. This is a difficult task that causes operator fatiguevery quickly, is not reliable, and hence is not used in practice. Tomitigate these problems, our invention digitizes the raw radar videosignal from the marine radar receiver and uses a PC-based radarprocessor with sophisticated processing to achieve significantlyimproved performance. The radar processor of the subject inventionincorporates a detection processor, a track processor, and a displayprocessor. Prior art processors have used significant amounts ofscan-to-scan integration to increase the SCR and thereby improvedetection sensitivity for small, slow-moving targets such as ice bergs,bergy bits, and capsized vessels or persons-in-water. These prior artsystems exploit the fact that the radars are mounted on vessels and thatsea clutter decorrelates over a relatively short time. Scan-to-scanintegration is not applicable to the fast-moving targets of interest ofthe present invention for two fundamental reasons: 1) the targets move,out of the radar resolution cell due to fast movement, and 2) the landclutter that dominates detection due to the fact that the radar sensorsare land-based does not decorrelate as quickly as sea clutter. As aresult, a different approach must be adopted to improve detectionsensitivity. Rather than emphasize the steady ground returns withscan-to-scan integration, they are preferably removed with an adaptiveclutter map. This is an important part of pre-detection radar processingwhen detecting in and around ground clutter. Ground clutter usuallyoriginates through mainbeam illumination when the antenna beam ispointed horizontally or looking down from a tower. Even for cases wherethe antenna is pointed up, for example, to detect birds, clutteroriginates from the antenna elevation sidelobes. After most clutter hasbeen suppressed, the detection processor of the present inventionproduces detections (also called plots) by setting lower detectionthresholds than conventional processors, and thus is able to detectsmaller targets. The consequence of using lower detection thresholds isthat an undesired, higher false alarm rate results, particularly due tothe strong clutter residual in the vicinity of the land-based radarsused in the present invention. The track processor of the presentinvention depends on sophisticated association and track filteringalgorithms that are designed to handle both the high false alarm rateand maneuvering targets. These approaches are unique to the presentinvention.

The plot-to-track association algorithm provides means to resolveambiguities produced by multiple targets, missed detections, falsealarms, and maneuvering targets, whereas the track filtering algorithmprovides high quality estimates of target dynamics for the associationalgorithms and for the display processor. While the track filteringalgorithm performs well with non-maneuvering targets, it uses specialalgorithms to handle maneuvering targets and this feature is unique tothe present invention. The track processor preferably uses asophisticated plot-to-track association algorithm called MHT [D. B.Reid, “An algorithm for tracking multiple targets”, IEEE Transactions onAutomatic Control, vol. AC-24, no. 6, December 1979, pp. 843-854] andpreferably uses an advanced track filtering algorithm called InteractingMultiple Model (IMM) filtering [G. A. Watson and W. D. Blair, “IMMalgorithm for tracking targets that maneuver through coordinates turns”,Proceedings of the SPIE (Society of Photo-Optical InstrumentationEngineers, vol. 1698, Signal and Data Processing of Small Targets, Apr.20-22, 1992, pp. 236-247]. It is understood that this invention includesschemes wherein the association algorithm is replaced by alternatetechniques known to those skilled in the art and described in theliterature including [S. S. Blackman, Multiple-Target Tracking withRadar Applications, Artech House, 1986], and wherein the track filteringalgorithm is replaced by alternate techniques known to experts in thefield and described in the literature including [S. S. Blackman,Multiple-Target Tracking with Radar Applications, Artech House, 1986].Furthermore, this invention also includes schemes where the associationand track filtering algorithms are combined into a single algorithm suchas the Probabalistic Data Association algorithm and its numerousvariants [Y. Bar-Shalom, “Tracking methods in a multitarget environment:survey paper”, IEEE Transactions on Automatic Control, vol. AC-23, no.4, August 1978, pp. 618-626], [S. S. Blackman, Multiple-Target Trackingwith Radar Applications, Artech House, 1986].

For homeland security and avian radar applications, one radar, or evenseveral independently operating radars is often not enough to provide ahigh-performance, composite tactical picture for a wide area ofinterest. For any single radar, there are gaps in coverage due toobstructions; and the area covered may not be a wide enough area. Thusthe second part of our invention is to network radars to a centralmonitoring station (CMS), and then integrate (and/or fuse) target datafrom all of them. A single system is suitable for monitoring ageographically close group of sites or even a fairly large waterway.Multiple systems can be further networked together to provide integratedcoverage of extended routes or border regions. Mobile systems areappropriate for monitoring regions needing more intermittent coverage.The benefits of fusion algorithms to further improve track quality willbecome apparent in the sequel. The networking of a number of land-basedradar sensors (each consisting preferably of a COTS marine radarcombined with a sophisticated radar processor) and the fusion of theirtarget data to provide improved tracking performance is a novel andunique feature of the present invention.

A major challenge of continuous, wide-area surveillance is the high costof human effort to monitor sensor displays. The networking of radarsensor target data to a CMS reduces the human costs significantly, sincemonitoring can be done far more efficiently at a single CMS than at theindividual radar sensor sites. However, further reductions in humanoperator costs are desirable, especially in applications such as borderpatrol, where vast regions of border have little or no target activityfor extended periods of time. In such cases, another feature of thepresent invention is particularly valuable. The track data produced bysystem of the present invention contains detailed (but compact)long-term behavior information on individual targets. For any givenscenario, these data can be automatically tested for suspiciousactivity, in order to generate alerts to security personnel. Because theinformation is detailed, alerts can reflect complex behavior, such ascollision predictions, origins and destinations of vessels, perimeterapproaches or violations, density of traffic, etc. The low-bandwidthtrack and alert information can be easily sent to central locations, anddirectly to end users, providing economical, effective monitoring. Anovel feature of the present invention is the provision of automatedalerts to remote users who require them. This enables the radarsurveillance system to run unattended with users alerted only whennecessary. Furthermore, track displays can be provided to remote usersto give them a clear picture of the situation when alerts arise. Theinvention preferably exploits COTS communication technology to providesuch remote alerts and displays inexpensively.

Further human cost reductions can be achieved with the present inventionthrough the provision of hardware and software to remotely control theoperation of each radar sensor, including the operation of each sensor'sradar processor, as well as the operation of its marine radartransceiver. A novel feature of the present invention is the remotecontrol of each radar sensor to reduce the human cost of operating andmaintaining the radar network of radar sensors.

The applications towards which the present invention is directed requirefurther research and development (R&D) in order to increase andestablish knowledge concerning target behavior. This knowledge can beused, for example, for automatic target identification. Off-lineanalysis of target data can be used with ground truth data to betterunderstand bird signatures, for example, which could then be used todevelop bird identification algorithms. In BASH applications, knowingthe kind of bird that is being tracked is valuable for forming anappropriate response (e.g. should aircraft delay take-offs and landingsor make an evasive maneuver to increase safety). In homeland securityapplications, target identification could be very useful in determiningwhether a real threat exists when a target approaches a securityperimeter near some critical infrastructure. Another example would be toperform off-line statistical analyses of target data in order to learnroutes and patterns characterizing criminal activity in border areas. Anovel feature of the present invention is the ability to continuouslystore complete target detection and track data over extended periods oftime in order to support such R&D activities. Another novel feature ofthe present invention is the ability to rapidly play back stored targetdata into the radar processor in order to study and analyze the data.Prior art systems (particularly those employing COTS marine radars) donot provide such support for R&D activities.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a block diagram of a radar sensor apparatus included in aradar surveillance system, in accordance with the present invention.

FIG. 2 is a block diagram of a radar controller that may be incorporatedinto the radar sensor apparatus of FIG. 1, in accordance with presentinvention.

FIG. 3 is a block diagram of a remote controller for a Furuno FR2155BBradar system, in accordance with the present invention.

FIG. 4 is a block diagram showing a radar network incorporating pluralinstances of the radar sensor apparatus of FIGS. 1, 2, and/or 3, inaccordance with the present invention.

FIG. 5 is a block diagram of radar network architecture in accordancewith the present invention.

FIG. 6 is essentially a block diagram showing a central monitoring siteor operations center using the radar network of the present invention.

DETAILED DESCRIPTION

A block diagram of a radar sensor apparatus 10 in accordance with thepresent invention is shown in FIG. 1. Characteristics of each block areas follows. The radar sensor apparatus 10 includes a radar device 12that is typically noncoherent and transmits pulses of constant width ata constant pulse repetition frequency (PRF) at X-band or S-Band. Radardevice 12 typically has either a continuously rotating or sectorscanning antenna 14. Antenna 14 is elevated to be several meters abovethe area to be monitored, and has a detection range of severalkilometers. COTS marine radars typically have these characteristics andare preferred for the present invention due to their availability,low-cost, and good antenna and transceiver characteristics.

Radar device 12 takes the form of a marine radar. A typical marine radaris noncoherent, transmits at X-band with 50 kW peak power, pulserepetition frequency (PRF) between 1 and 2 kHz and with pulse widthbetween 0.1 and 1 μs. It has a 2 m antenna with a narrow azimuthbeamwidth and a wide elevation beamwidth, rotates at 24 RPM, and has upto 165 km range. A radar such as this retails for around $50,000. Marineradar configurations are based on choosing a peak power/maximum-rangevalue and an antenna size. Radars with peak powers up to 10 kW typicallyretail for less than $10,000. The lower-power radars can be purchasedfor as little as two or three thousand dollars making them very costeffective.

Notwithstanding these typical characteristics, radars with otherfeatures known to those skilled in the art (e.g. multi-frequencyoperation) could be employed without departing from the spirit of theinvention.

In some applications, it is important to use a specialized antenna 14 tomeet requirements. An avian radar application, for example, oftenrequires bird height information. A typical marine radar antenna with a20° elevation beamwidth does not provide accurate enough heightestimates in these cases. As a result, other antennas may be preferred.In the article [Nohara, T J et al, Affordable avian radar surveillancesystems for natural resource management and BASH applications, 2005 IEEEInternational Radar Conference, May 9-12, 2005, Arlington, Va.], a 4°pencil beam dish antenna is described that has been successfully testedin the field with an implementation of the radar sensor of the presentinvention. This antenna provides better height estimates of birds butits coverage is limited. To solve the coverage problem, antenna 14 maybe an elevation-monopulse antenna to provide simultaneously good heightestimates with full coverage in elevation. The present inventionprovides for the integration of such an antenna into the radar sensorapparatus 10. While a phased array antenna could be integrated into theradar sensor 10 of the present invention, it is not a preferredembodiment of the present invention due to the significantly higher costanticipated for such an antenna. In addition, it is not clear that thevolume search rate of such a two-dimensional antenna could satisfytarget update requirements.

As illustrated in FIG. 1, a digitizer 16 is connected to an output ofmarine radar device 12 for collecting radar video samples from eachpulse, at sampling rates and over range intervals appropriate for theoperational mode. Digitizer 16 is preferably a PC card mounted on a busof a computer 18, which is preferably a commercial off-the-shelf (COTS)PC. The PC computer 18 can run any standard operating system, butpreferably runs a Microsoft Windows™ operating system. The digitizer 16itself is preferably a COTS product to further reduce the radar sensorcost. The digitizer 16 preferably samples the radar video signal at12-bits and operates in real-time. The digitized signals are thefull-bandwidth, unprocessed radar signals captured in real-time tocreate a fully digital radar sensor in which the radar's signalprocessing and operating characteristics are determined by a radarprocessor 20.

Radar processor 20 is implemented as generic digital processing circuitsof computer 18 modified by programming, or configured by software, toaccomplish the functions described hereinafter. Radar processor 20includes a detection processor or plt extractor 22, a multi-target trackprocessor 24 and a display processor 26 all of which are preferablyimplemented in real-time by software that runs on the COTS PC 18. Thesoftware is preferably written in C/C++, and possibly assembly, and usesmulti-threaded programming to provide a highly responsive application aswell as for computational efficiency. The software also preferablyexploits the Single Instruction Multiple Data (SIMD) capabilities ofmodem processors to considerably improve processing speed. The softwarecould be developed in any language known to those skilled in the artwithout departing from the spirit of this invention.

Detection processor 22 declares the presence and location of targetspreferably on each radar scan. Track processor 24 sorts the time-seriesof detections (also called plots) into either tracks (confirmed targetswith estimated dynamics) or false alarms. The processed informationproduced by radar processor 20 can be presented to the operator on alocal display 28 that is part of display processor 26. This informationmay include scan-converted video, target data including detection dataand track data, maps, user data (e.g. text, push pins) etc. Operatorcontrols 30 may be local as well and provide a graphical user interfacefor the local user to control the operation of the radar processor 20.

The radar processor 20 performs radar signal processing functions knownto those skilled in the art such as scan-conversion, adaptiveclutter-map processing to remove ground and weather clutter, sectorblanking to suppress detections in regions that are not of interest,constant false alarm rate (CFAR) processing, and digital sensitivitytime control (STC). These functions may be included in either thedetection processor 22 or the display processor 26, but preferably areincluded in both so that the user display can be optimized for the userwhile the detection processor can be optimized for detection andtracking performance.

Conventional radars employing automatic detection and trackingalgorithms typically set the detection threshold high enough to achievea probability of false alarm (PFA) to 1 in 10⁶ resolution cells or less.For a radar display extending 50 km in range with a 100 m rangeresolution and 1° azimuth resolution, this translates to about 1 falsealarm every 5 scans or 12 seconds (typical marine radar scan rates are24 RPM). In contrast, low detection thresholds are a special feature ofthe detection processor 22 and are used in order to increase thesensitivity of the radar, allowing smaller targets to be detected. Anunwanted side effect is that the false alarm rate increasessubstantially, making it more difficult for tracking to perform. Forexample, the PFA could drop 3 orders of magnitude from typical settingsto say 10⁻³ resulting in 180 false alarms per scan or 72 false alarmsper second. This is a huge stress on tracking. To mitigate this effect,as well as to successfully track through maneuvers without degradationsin track quality, the track processor 24 preferably includes multiplehypothesis testing (MHT) tracking with interacting multiple model (IMM)extended Kalman filtering as described earlier, and which are furtherdescribed in [D. B. Reid, “An algorithm for tracking multiple targets”,IEEE Transactions on Automatic Control, vol. AC-24, no. 6, December1979, pp. 843-854], [G. A. Watson and W. D. Blair, “IMM algorithm fortracking targets that maneuver through coordinates turns”, Proceedingsof the SPIE (Society of Photo-Optical Instrumentation Engineers, vol.1698, Signal and Data Processing of Small Targets, Apr. 20-22, 1992, pp.236-247]. These advanced processing algorithms often found in militaryradars yields the performance of much higher-priced systems and havebeen shown to work well under these high false alarm rate conditions.

The display processor 26 provides a real-time display. Preferably, a mapis integrated with the radar display and provides a background on whichis overlaid geo-referenced radar data, including target data (tracks anddetections), target echo trails, as well as scan-converted radar videoin the form of a PPI display. These features enable target behavior tobe more easily understood, where the display processor 26 can be viewedas a geographical information system (GIS). Cursor position in latitudeand longitude or UTM coordinates is continuously read out in the statusbar, and numerous display features common to marine radars such aselectronic bearing lines and virtual range markers are available. Smallsymbols at the location where the threshold is exceeded indicatedetections. A history of detections from previous scans can be shown,with fading intensities indicating scan time (the current scan'sdetections are the brightest). Tracks are indicated by a differentsymbol drawn at a target's current position with a line emanating fromthe symbol indicating the heading. The operator can select any track onthe screen, and the system will display target information such asposition, speed, heading, track stage, track uncertainty, echo size andintensity. These target attributes can also be used for the study andclassification of targets of interest, and for multi-sensor fusion.Detection and track data are rich with target attributes that areavailable for viewing by the operator in real-time. At any instant intime, the track histories provide situational awareness of recentactivity. Any suspicious behavior (e.g. perimeter crossings) can berecognized, and communicated to authorities.

Many of the aforementioned radar processor features as well as featuresnot mentioned above are described in [Weber, P et al., Low-cost radarsurveillance of inland waterways for homeland security applications,2004 IEEE Radar Conference, Apr. 26-29, 2004, Philadelphia, Pa.] and[Nohara, T J et al, Affordable avian radar surveillance systems fornatural resource management and BASH applications, 2005 IEEEInternational Radar Conference, May 9-12, 2005, Arlington, Va.]. Forexample, the benefits of the low detection thresholds to improve smalltarget detection sensitivity are demonstrated with real data in [Weber,P et al., Low-cost radar surveillance of inland waterways for homelandsecurity applications, 2004 IEEE Radar Conference, Apr. 26-29, 2004,Philadelphia, Pa.] along with the ability of the track processor 24 totrack reliably through target maneuvers without increasing trackuncertainty. Clutter-map processing is demonstrated in [Nohara, T J etal, Affordable avian radar surveillance systems for natural resourcemanagement and BASH applications, 2005 IEEE International RadarConference, May 9-12, 2005, Arlington, Va.] to reject ground clutter sothat birds can be detected along with a specialized target echo trailsdisplay mode that is a feature of the present invention.

A feature of the digital radar processor 20 of the present invention isthe implementation of automated alerts based on target behavior inferredfrom track data. Target behaviors such as perimeter breach, collisionprediction or any complex behavior can be defined. When operating as anautomated monitoring system, security perimeters are preferably defined.The radar processor then determines when targets approach and crossthese perimeters, and issues appropriate alert responses. Preferably,target detection, tracking and threat recognition algorithms arecustomized for specific threats and scenarios. Alerts can include anaudible alarm and display indication to an operator, or a transmittedmessage to a remote user. Transmitted messages are preferablycommunicated over a network to remote users using networking andcommunication methods and technology known to those skilled in the art.Preferably, alerts can be issued as text messages or e-mails directed topagers, cell phones, personal data assistants, Blackberrys™ etc. usingCOTS technology. Alerts can minimize required operator resources even tothe point of permitting some systems to run 24/7 unattended.

A recorder 32 shown in FIG. 1 can store the received radar video samplesonto disk or tape. Target data including track data and detection datacan also be recorded. Target data is a more compact and convenientalternative to raw radar video and can easily be stored continuously,24/7, without stressing the storage capacity of a COTS PC. These samedata can be remoted over a network 34; full-fidelity raw video, however,generally requires very high-speed networks. Target data, on the otherhand, can be handled on low-speed networks, including real-timedistribution over COTS wireless networks and over the Internet throughinexpensive COTS networking hardware. The stored data (in either rawformat or target data format) can subsequently be played back throughany computer running the radar processor software; it is not necessarythat it be connected to a radar. This feature is useful for off-lineanalysis, investigations, evidence for use in prosecutions, etc. Targetdata can be archived for longer-term investigations. The recorder 32stores target data in accordance with operator selections. The recorder32 supports continuous writing of target data directly to a database 36(as well as to other file formats). The database 36 can reside locallyon the radar processor computer, as indicated by a phantom connection38, on another computer on the network, or on both. The database 36 isused preferably for post processing, for interaction with externalgeographical information systems (GIS) systems, for remote radardisplays, for support for web services, and for further research anddevelopment (e.g. to investigate and develop target identificationalgorithms).

Another feature of the radar processor 20 is that it can be controlledremotely over network 34 (schematically shown as a bus in FIG. 1), whena network connection is available. Radar processor control functions areimplemented preferably as a web service, or alternatively, by using avirtual network console (VNC) so that the PC keyboard (not shown) anddisplay 28 of radar processor 20 can be run remotely. COTS VNC serversoftware runs on the radar processor PC and client VNC software runs onthe remote end of the network 34. If the network 34 includes one or moresegments on the Internet, a virtual private network (VPN) is preferablyestablished using COTS technology known to those skilled in the art. Inthis manner, the radar processor 20 can be remotely controlled fromanywhere on an established network, using COTS software and hardware.

If the radar processor 20 is to be controlled remotely over the network34, it becomes important to also be able to control remotely the marineradar functions as well. These functions include, preferably,power-on/off, transmit/standby, and operating range selection.Unfortunately, COTS marine radars designed for marine use do not comewith network-enabled remote control features. As a result, a feature ofthe radar sensor of the present. invention is a radar controller 40 tocontrol the marine radar through a network-enabled software interface.The radar controller 40 includes hardware (e.g. switches, control codes,etc.) that integrates with the marine radar to replicate control signalsprovided by the radar manufacturer. This hardware is controllable bysoftware that preferably runs on a COTS PC, and may be the same COTS PCthat houses the radar processor. The software provides either a userinterface or programmer's interface to control the aforementioned radarfeatures. The software can be accessed over a network (as illustrated inFIG. 1) either as a web service or through a VNC connection as describedearlier.

Marine radars typically remember their state during power down.Therefore, when the radar is powered up, it comes back in its previousstate (which includes the range setting). If the marine radar is to becontrolled remotely, then it is important that the operator is certainof the state of the radar at all times since the radar processorperformance depends on this. A novel feature of the radar controller 40is its preferred use of the radar's own display 28 to confirm the radarstate. The radar's local display video, schematically represented at 42,is captured preferably using COTS frame-grabber technology and madeaccessible remotely through the radar controller software. In this way,the remote user can use the software to change the radar's state and canconfirm immediately that the state has changed as requested by observingthe remoted radar display. In FIG. 2, a block diagram of the radarcontroller 40 is shown. The diagram shows two logical components, namelythe radar controller 40 with interface 44, and the marine radar device12. The radar controller 40 is ideally composed of both COTS hardwareand software with the addition of original hardware and software.Controller 40 utilizes a hardware and software interface customized forthe particular radar type to be controlled. Where possible, the existingradar control is preserved so that the addition of the computerautomation does not interfere with standard manual operation of theradar system. Within the interface 44, the controller is connected to apower switch or relay 46 for enabling remote control of the power supplyto radar device 12, and to a command combiner 48 for controlling datatransmission functions and antenna range. The interface 44 also includesa video splitter 50 and a video capture module 52 for capturing theradar's local display video 42.

FIG. 3 shows a preferred implementation 54 of the radar controller 40 ofFIG. 2 as applied specifically to a COTS Furuno 2155BB radar system 56.The controller 54 uses serial codes for a variety of functions and relaycontact switches for other functions. The emulation of other radarcontrol functions may require the use of digital to analogue (D/A)converters, analog to digital (A/D) converters, digital I/O or otherconversion interfaces in order to enable computer control. Thecombination of hardware interfaces and software application interfaceare then network-enabled using standard open web services such as XMLRemote Procedure Calls (XML-RPC) or SOAP over a standard networktransport protocol, such as HTTP.

Components of the COTS Furuno 2155BB radar system 56 in FIG. 3 thatperform the same functions as components shown in FIGS. 1 and 2 arelabeled with like reference designations. FIG. 3 also depicts a Furunoprocessor 57, a Furuno keyboard 58 and an ancillary radar processor 60.

One or more radar sensor apparatuses 10 as described above withreference to FIGS. 1-3 can be connected to network 34 to distributeinformation to remote users. The radar processor architecture supportsreal-time communication of target data to remote sites usinglow-bandwidth, COTS network technology (wired or wireless). Since thetarget data contain all of the important target information (date, time,position, dynamics, plot size, intensity, etc.), remote situationalawareness is easily realized. The all-digital architecture facilitatesnetworking of radar target data and control functions to a centralmonitoring station (CMS) 60 (FIG. 4) to consolidate monitoring resourcesfor an entire radar network, thereby minimizing operating cost andproviding for low-cost, high-performance radar networks. The use of opennetwork protocols such as TCP/IP and HTTP allow the delivery of theradar data anywhere over the Internet. It also makes available a numberof standard web service protocols that can be used on the network toprovide a software application programming interface (API). One exampleof this is the use of XML-RPC in the radar controller 40, 54 to create anetwork-enabled API that is accessible over HTTP. A web server is thenused to provide a client interface to a remote user.

The web server functions as both a web client application to the XML-RPCserver to perform the radar control functions, as well as a web serverapplication to provide a user-friendly graphical interface to a remoteuser with a client web browser. This same principle is applied to otherradar data services, such as the web services server interface to aTCP/IP networked SQL database containing a repository of past and livereal-time radar data.

FIG. 4 shows a conceptual diagram of the computer radar network 34. Oneor more radar sensors 10 send their target data to one or more CMS 60(which could be co-located with any of the radar sensors 10). The targetdata consists of detection data, track data and/or alerts. Raw radarvideo data could also be sent to the CMS 60 in real-time if a suitablenetwork was available, but preferably, target data is sent. Other typesof surveillance sensors (e.g. sonar) can also be on the network 34. Thenetwork 34 and its software are typically COTS. The CMS 60 has afusion/display processor 62 (FIG. 5) that processes, combines, displaysand archives the data. Integrated tactical information, includingdisplays and alerts, is provided. Track and detection data from theseparated radar sensors 10 may be fused to take advantage of theirspatial diversity and improve the radar network performance beyond thatof the radar sensors themselves using multi-sensor data fusion methodsknown to those skilled in the art. This takes advantage of the spatialdiversity of the sensors, and improves the radar network performancebeyond that of the radar sensors 10 themselves. Data can also beaccessed and integrated from other private or public networks (e.g.military, NEXRAD) as well.

FIG. 5 shows a preferred embodiment where the radar network 34 isimplemented via the global computer network 64 known as the “Internet”,with only a single radar apparatus 10 shown. The same configuration ofradar processor 20 plus radar controller 40 (or 54) is replicated forother sites. Each site is connected to the Internet network 64 using afirewall and router device 66. (It is not necessary to use the Internet64 as part of the network; a completely dedicated or private networkcould obviously be used as well.) This configuration enables eachindependent site to connect and send radar data continuously and in areal-time fashion to a remote radar data server 68 and to enter it intoa common SQL database server. A single SQL database server is capable ofreceiving radar data from multiple related Radar Processor sitessimultaneously. The centralized pooling of radar data from the multipleradar sites allows for integration or fusion of related radar data bythe CMS Fusion/Display processor 62. An example of this is theprocessing of radar target tracks that cross the radar coverage areascanned by the radar antenna 14 of physically adjacent or related radarsensors 10.

The use of a standard open high-performance networked SQL databaseserver in the radar data server 68 further maximizes the flexibility inproviding the data services to multiple CMS users on the network 34while keeping costs low. The asynchronous messaging within the SQLdatabase allows the radar processor 20 to indicate when a new scan ofdata is available inside the database. This signals the fusion/displayprocessor 62 of any CMS 60 to monitor a particular radar processor 20 toupdate its display in real-time with the latest data. The CMSfusion/display processor 62 need not be local to the radar data server68 and may be located anywhere on the network 34, whether realized viathe Internet 64 or a private network (not separately illustrated). Inaddition to monitoring live radar data, the CMS 60 also provides thecapability to play back past recorded radar data. The functionality isanalogous to that of a COTS hard-disk based Personal Video Recorders(PVR) such as TiVO. The CMS 60 may similarly allow a user to:

-   -   choose to watch a particular live radar data feed coming from a        single or multiple radar processors 20, with Picture-In-Picture        type monitoring,    -   pause the display,    -   continue the display (now delayed from live by the pause time),    -   rewind or fast-forward through the data with display at 2×, 4×,        or 8× rates,    -   play back at ⅛×, ¼×, ½×, 1×(real-time), 2×, 4×, or 8× speed,    -   play back data from a particular time stamp or index marker,    -   choose another pre-recorded experiment from menu, and    -   resume monitoring of the live data feed.

A handheld remote control device similar to that of a PVR, VCR, or DVDplayer preferably provides the operator with a familiar human deviceinterface. Such high-performance features added to a radar network asdescribed above are unique to the present invention, all at affordablecost by exploiting open and COTS technologies.

The network-enabled XML-RPC API of the radar controller 40 (or 54) givesprogrammatic access to the radar by an engineering maintenance console70 (FIG. 5). Operations across multiple sites may be scheduled ahead oftime and executed remotely by software. An example of this is thescheduling of monitoring only during a nightly interval. Another exampleis the automated change of radar parameters during daytime monitoring.

In a similar manner to the use of sophisticated radar processing andtracking, the CMS fusion/display processor 62 shown in FIG. 5 can fusetarget data from a radar network 34 to enhance the performance of thesenoncoherent low-cost radar systems, and have them approach the level ofmore expensive coherent radar systems. Some of the performanceimprovements achievable through integration and fusion of data fromradar networks include but are not limited to the following:

-   -   Multi-radar fusion to improve track accuracy, continuity,        quality, etc.    -   Spatial diversity against target fluctuations in RCS (necessary        for small targets)    -   Spatial diversity for shadowing due to geographic obstructions    -   Spatial diversity to cover extended borders, equivalently        increasing radar coverage

The richness of the target data available from each radar sensorapparatus 10 in the network allows much flexibility when such data isrequired to be combined or fused for a wide-area display. Depending onthe level of fusion required (which will be driven by application,geography and target density), the target data permits both contact(detection) and track-level combination of data. The following(non-exhaustive) list provides some examples of possible fusion methodsthat may be applied to the available data:

-   -   Synchronous fusion (contact-level)    -   Parallel fusion (contact-level)    -   Best track (track-level)    -   Covariance intersection (track-level)    -   Information fusion (track-level)    -   Reasoning and knowledge-based approaches

As is known to those skilled in the art, numerous methodologies andalgorithms exist for combining such data, and new techniques are alwaysbeing developed. The following references provide examples of suchmethods [D. L. Hall, J. Llinas (Eds), Handbook of Multisensor DataFusion, CRC Press, 2001], [Y. Bar-Shalom (Ed.), Multitarget-MultisensorTracking: Advanced Applications, Vol. I, Artech House/YBS Publishing,1998.]and [D. L. Hall, Mathematical Techniques in Multisensor DataFusion, Artech House, Norwood Mass., 1992]. The sophistication of theaforementioned radar detection and track processing, as well as thecareful archiving and transmission of this data, ensures that the CMSfusion/display processor 62 can incorporate and evaluate any applicablefusion strategy, including new and emerging methods. Another significantfeature of the present radar surveillance system is the ability tocustomize the level and extent of the integration and fusion available,which is achievable through the rich information that has been producedand recorded by the radar detection processor 22 and tracker processor24.

FIG. 6 illustrates an example of a radar network 34 in accordance withprinciples elucidated herein. Seven radar sensors 10 schematicallydepicted as antennas 14 are assumed to be geographically separated tocover a wide-area of surveillance. Land-based installations are assumed,and antenna towers are made high enough to reduce blockage to acceptablelevels, but low enough to be cost-effective and covert. Portable andmobile systems are also possible. In this example, two CMS's 60 areshown, one indicated as a command and control CMS 60 a and the other asa secondary operations center 60 b. Ten radar workstations 72 are shownin the one CMS 60 a and a single radar workstation 74 in the other 60 b.Each radar workstation 72, 74 can run the CMS fusion/display processorto create an integrated tactical surveillance picture from target dataassociated with a particular radar sensor 10, or multiple radar sensors.These support multiple operators with specific missions. A dedicateddisplay processor 76 that provides a completely integrated tacticalpicture preferably using all of the available radar sensors 10 drives alarge war-room type display. Each radar workstation 72, 74 is adedicated workstation or workstations 72, 74 could also serve as theengineering maintenance console 70.

Another novel feature of the present radar surveillance system is theprovision of a remote integrated tactical display to a mobile user. Forexample, consider the case where law enforcement personnel areattempting to thwart an illegal activity in a border patrol application.The law enforcement personnel are located on mobile vessels on the waterborder. Using their on-board marine radar provides little or nosituational awareness for reasons described earlier.

Furthermore, line of sight is extremely limited because of the lowheight of the marine radar above the water. Instead, the law enforcementvessel receives an integrated tactical picture from the CMS 60 over awireless network 34. The law enforcement vessel has an on-board COTS PCrunning a remote CMS Display Client that provides the integratedtactical picture created by the CMS Fusion/Display Processor.Preferably, the vessel's current location is shown on the tacticalpicture via a GPS input. The CMS 60 (or 60 a, 60 b) simply routes fusedtarget data produced by the CMS fusion/display processor 62 over awireless network 34 to the CMS Display Client. The law enforcementvessel gains the benefit of the performance of the entire radar network.Even if only a single radar sensor 10 is available and the radarprocessor 20 remotes its target data to the CMS display client directly,the vessel will have the radar visibility of a land-based, tower-mountedmarine radar and sophisticated processing that far exceed thecapabilities of the on-board marine radar.

Sighting land-based radar sensors to maximize coverage is an importantfactor in network design and resulting radar network system performance.Sighting a radar for coverage can be a labor intensive and henceexpensive process. In accordance with another feature of the radarprocessor of the present invention, this labor cost is minimized. Thedisplay processor 26 includes the ability to overlay PPI radar video(with now ground clutter suppression) on top of a geo-referenced map.Since the radar sensors 10 are land-based, this overlay will immediatelyshow the presence of ground clutter, or its absence due to blockage orshadowing. Wherever ground clutter is present and overlaid on the map,coverage is available, where ever it is not, coverage is not available(at least for targets low to the ground). Moving the radar around in amobile vehicle (e.g. a truck with a telescopic mast) and creating thesecoverage maps in real-time is a convenient, efficient, andcost-effective way of sighting the radar sensors that will form a radarnetwork.

One of the key features of the present radar surveillance system is theexploitation of COTS technologies to keep the radar sensors and radarnetwork low-cost. Not only is initial purchase cost made affordable withthis approach, but maintenance and replacement are also characterized byshort lead times, multiple suppliers, and reasonable prices. The systemsin accordance with the present invention deliver high performance withfeatures tailored to customer needs while minimizing the three majorcomponents of cost: purchase cost, maintenance cost and operationalcost.

A final feature of the present radar surveillance system is its softwarere-configurability which permits extensive customization to adapt itsfeatures to specific applications other than those described herein,with reasonable levels of effort. This will permit access to smallermarkets since minimum economic quantities of customized systems will besmall. The software platform architecture also permits upgrades, featureaddition, and target market customization.

Particular features of our invention have been described herein.However, simple variations and extensions known to those skilled in theart are certainly within the scope and spirit of the present invention.

We claim:
 1. A historical radar data analysis method comprising:operating at least one radar apparatus to transmit radar pulses; furtheroperating said at least one radar apparatus to receive radar echoes;additionally operating said at least one radar apparatus to generate,from the received radar echoes, radar target data including radar targettracks; operating a radar data server to continuously receive in areal-time fashion said radar target data including said radar targettracks generated by said at least one radar apparatus, said radar dataserver including a SQL or structured query language database, theoperating of said radar data server including operating said SQL orstructured query language database to organize, insert and store thereceived radar target data including said radar target tracks in areal-time fashion as organized radar target data (i) so that saidorganized radar target data including said radar target tracks are madeavailable for immediate access from said database as real-time targetdata by a radar display or processor that operates in a real-timefashion, continuously being updated by said radar data server, and (ii)so that said organized radar target data stored in said database can bequeried for subsequent access as historical target data, said historicaltarget data being taken from the group consisting of (i) said radartarget tracks and (ii) threat alerts; operating a user application on acomputer to communicate, to said radar data server, a request for targetdata from said historical target data; further operating said radar dataserver to receive said request, select and extract the requested targetdata from said database and send said requested target data to therequesting user application; and further operating said user applicationon said computer to receive, from said radar data server, said requestedtarget data from said historical target data in said database.
 2. Themethod in claim 1 wherein said requested target data pertain to targetstaken from the group consisting of (i) non-cooperative targets withcollision predictions, (ii) non-cooperative targets with predeterminedorigins or destinations, (iii) non-cooperative targets approaching asecurity perimeter, (iv) non-cooperative targets violating apredetermined security perimeter, and (v) non-cooperative targets with apredetermined traffic density.
 3. The method in claim 1 where said radardata server includes a web server and said user application is a webbrowser.
 4. The method in claim 1 wherein said historical target datapertains at least in part to non-cooperative targets including at leastone member of the group consisting of watercraft, snowmobiles, birds,aircraft and vehicles detected and tracked by said at least one radarapparatus.
 5. The method in claim 1, further comprising additionallyoperating said user application on said computer to provide, from saidselected historical target data, situational awareness for homelandsecurity applications and bird aircraft strike hazard applications, theadditional operating of said user application including analyses beingtaken from the group consisting of (i) statistical analyses, (ii)analyses to increase and establish knowledge on target behaviour, (iii)research and development on target identification algorithms, and (iv)provision of evidence for use in legal prosecutions.
 6. The method inclaim 5 wherein said additional operating of said user application andsaid analyses of said historical target data increase knowledge ontarget behavior, said knowledge being information on target routes andpatterns.
 7. A method for use in historical radar data analysis,comprising: operating at least one radar apparatus to transmit radarpulses; further operating said at least one radar apparatus to receiveradar echoes; additionally operating said at least one radar apparatusto generate, from the received radar echoes, radar target data includingradar target tracks; operating a radar data server to continuouslyreceive in a real-time fashion said radar target data including saidradar target tracks generated by said at least one radar apparatus, saidradar data server including an SQL or structured query languagedatabase, the operating of said radar data server including operatingsaid SQL or structured query language database to organize, insert andstore the received radar target data including said radar target tracksin real-time fashion as organized radar target data (i) so that saidorganized target data stored in said database is made available forimmediate access from said database as real-time target data by a radardisplay or processor that operates in a real-time fashion, continuouslybeing updated by said radar data server, and (ii) and so that saidorganized radar target data stored in said database can be queried forsubsequent access as historical target data, said historical target dataincluding said radar target tracks; additionally operating said radardata server to accumulate, in said database, said radar target data asorganized radar target data over time resulting in a build-up andlong-term storage of historical target data in said database; affordingaccess to said database by at least one user application, the affordingof access including operating said radar data server to receive arequest from said user application for target data from said historicaltarget data; and in response to the request from said user application,operating said radar data server to select and extract the requestedtarget data from said database and send said requested target data tosaid user application.
 8. The method in claim 7, further comprisingoperating a user application on a computer to analyze the requestedtarget data to provide situational awareness for homeland securityapplications and bird aircraft strike hazard applications, the operatingof said user application including analyses taken from the groupconsisting of (i) statistical analyses, (ii) analyses to increase andestablish knowledge on target behaviour, (iii) research and developmenton target identification algorithms, and (iv) provision of evidence foruse in legal prosecutions.
 9. A method for use in historical radar dataanalysis, comprising: operating at least one radar apparatus to transmitradar pulses; further operating said at least one radar apparatus toreceive radar echoes; additionally operating said at least one radarapparatus to generate, from the received radar echoes, radar target dataincluding radar target tracks; operating a radar data server tocontinuously receive in a real-time fashion said radar target dataincluding said radar target tracks generated by said at least one radarapparatus, said radar data server including an SQL or structured querylanguage database, the operating of said radar data server includingoperating said SQL or structured query language database to organize,insert and store the received radar target data including said radartarget tracks in real-time fashion as organized radar target data (i) sothat said organized target data stored in said database is madeavailable for immediate access from said database as real-time targetdata by a radar display or processor that operates in a real-timefashion, continuously being updated by said radar data server, and (ii)and so that said organized radar target data stored in said database canbe queried for subsequent access as historical target data, saidhistorical target data including said radar target tracks; additionallyoperating said radar data server to accumulate, in said database, saidradar target data as organized radar target data over time resulting ina build-up and long-term storage of historical target data in saiddatabase; affording access to said database by at least one first userapplication, the affording of access including operating said radar dataserver to receive a request from said at least one first userapplication for real-time target data from said radar target data; andin response to the request from said at least one first userapplication, operating said radar data server to select and extract therequested real-time target data from said database and send saidrequested real-time target data to said at least one first userapplication; affording access to said database by at least one seconduser application, the affording of access including operating said radardata server to receive a request from said at least one second userapplication for target data from said historical target data; and inresponse to the request from said at least one second user application,operating said radar data server to select and extract the requestedtarget data from said database and send said requested target data tosaid at least one second user application.